EVANSTON--Sometimes, games can swing on one play. A single snap can not only determine the outcome of the contest but change the entire complexion of the game.

One such play occurred in the third quarter of Northwestern's 34-24 loss to Penn State, and it sealed the Wildcats' fate and turned what had been a track meet into a defensive struggle.

And for the second straight week, the pivotal play for Northwestern was an interception of quarterback Dan Persa.

"They (Penn State) made some big plays and obviously that interception for a touchdown kept it from being a one-score game," said coach Pat Fitzgerald.

It did much more than that.

Northwestern's offense ran roughshod over the 6th-ranked defense in the country in the first half. The Wildcats in the first 30 minutes rolled up 281 yards and 24 points, more than all but one team had put on the board against the Nittany Lions in a full game all season (that team was No. 2 Alabama, with 27). Persa was 13-of-16 passing for 180 yards and a touchdown, and Kain Colter added a boost to the running game with 61 first-half yards, including a 46-yard scamper and a 4-yard TD run.

Northwestern's defense was as bad as the offense was good, allowing a Lion attack that scored just 13 and 16 points in wins over Iowa and Indiana, respectively, to ring up 27 in the first 30 minutes. The Lions are not built for quick strikes and big plays but came up with a 42-yard run and a 45-yard pass for a touchdown, and took all of 40 seconds to drive the field for a TD with :07 left in the half.

The offensive bonanza looked like it would continue in the second half. The Wildcats came out in the third quarter and picked up right where they left off, marching 62 yards in seven plays to the Penn State 28.

That's when the game took a 180-degree turn.

Persa dropped back and fired a pass over the middle that was tipped at the line of scrimmage. Penn State linebacker Gerald Hodges picked off the fluttering knuckler and returned it 63 yards to the Northwestern 19.

One play later, Silas Redd broke over the right side for a touchdown to extend Penn State's lead from 3 to 10 points.

That play not only dropped a shot put onto Penn State's side of the game scale. It also completely altered the pace and character of the game.

Penn State and Northwestern had a combined 11 possessions before that fateful drive and scored on 10 of them. The only "drive" that didn't result in points was Northwestern's last, when Persa took a knee with :07 left.

After Redd's touchdown, however, the two teams combined for 10 more drives, and those resulted in eight punts, a turnover on downs and three kneel-downs in victory formation by Penn State.

The wide-open barnburner had suddenly turned into a tight struggle. The stat sheet, not surprisingly, reflected the radical shift in the game. While the first half ended 27-24, the second was 7-0. Northwestern's yardage total went from 281 in the first half to 134 in the second, and Penn State's from 293 to 118.

Fitzgerald saw good and bad on both sides of his team's split personality.

Offensively, he called the game a "tale of 'what ifs. We had plenty of opportunities, especially in the second half to make the plays that winners do, and unfortunately we weren't able to accomplish that."

On the flip side, though, he saw some progress from a defensive secondary that had been ripped by big plays over its three previous losses due to lapses in communication.

"We didn't have a whole lot of discussion on the boundary for the first time in a month about poor communication," he said. "So that's a positive."

Cat scratches

Looking for combinations: Northwestern's starting defense had four new faces on Saturday night as Fitzgerald continues to look for a more effective lineup. Defensive end Vince Browne, linebackers Bryce McNaul and David Nwabuisi, and safety Ibraheim Campbell were benched in favor of Quentin Williams, Chi Chi Ariguzo, Damien Proby and David Arnold, respectively. "I think the number one motivator in the world is a watch, it's called the bench," said Fitzgerald. "If you don't figure it out, if you're not playing consistently, I've got one of the best seats at Ryan Field and you're going to stand next to me. That's not a threat, that's just how we're going to get better."

Nothing serious: Persa limped off the field in the fourth quarter with what Fitzgerald called a foot injury and didn't return. It was his left foot, however, and completely unrelated to the right Achilles tear he suffered last season. "He probably could have gone back in the game," said Fitzgerald.

Another major milestone for JoePa: Fitzgerald paid tribute to Penn State coach Joe Paterno for recording his 408th win on Saturday night, tying Grambling legend Eddie Robinson on the all-time list. Fitzgerald is just getting tired of the Lions coach, who is in his 46th year in State College, reaching those milestones against his team. Paterno notched his 400th win against Northwestern last year.

Taking time: Fitzgerald defended his decision to call timeout with :56 left in the first half, calling it an aggressive move. Northwestern went on to score a field goal to extend its lead to 24-20, only to see Penn State march back down the field in 40 seconds to retake the lead, 27-24, before the half. He added that he expected to get second guessed about his decision.

Where's Smith? Fitzgerald said that tailback Adonis Smith did not play against Penn State because he was "dinged up" at practice during the week.